JAVA反射其实就是那么一回事

package Test2016.demo;

import java.lang.reflect.Field;

public class Demo4 {

    public static void main(String[] args) throws Exception {
        
        Student stu = new Student();

        Field[] fields = stu.getClass().getDeclaredFields();
        
        for (Field f : fields) {
            f.setAccessible(true);　　//设置是否允许访问，不写运行会报错
            
            if (f.getName() == "name") {
                f.set(stu, "java");
            } else if (f.getName() == "age") {
                f.set(stu, 20);
            }
        }
        System.out.println(stu);    //输出:java:20
    }
}


class Student {
    
    private String name;
    
    private int age;
    
    public Student() {
        this.name = "zhangsan";
        this.age = 10;
    }
    
    //重写toString方法,否则输出:Test2016.demo.Student@e53108
    public String toString() {
        return this.name + ":" + this.age;
    }
}

package Test2016.demo;

import java.lang.reflect.Method;


public class Demo4 {

    @SuppressWarnings("unchecked")
    public static void main(String[] args) throws Exception {
        
        Student stu = new Student("zhangsan", 21);
        
        Class c = stu.getClass();
        
        //getMethod()方法需要传入方法名和方法所带参数的参数类型
        Method method = c.getMethod("score", int.class);
        
        //invoke()表示调用的意思,需要传入对象和参数
        method.invoke(stu, 100);
        
        Method m = c.getMethod("say", String.class);
        //这里的null表示不由对象调用,也就是静态方法,把null换位stu也是可行的
        m.invoke(null, "hello java!!!");
    }
}


class Student {
    
    private String name;
    
    private int age;
    
    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
    
    public void score(int score) {
        System.out.println(this.name + " 考了 " + score + " 分");
    }
    
    public static void say(String str) {
        System.out.println("刚才我说了:" + str);
    }
    
    @Override
    public String toString() {
        return this.name + "-" + this.age;
    }
}

package Test2016.demo;

import java.lang.reflect.Array;


public class Demo4 {

    public static void main(String[] args) throws Exception {
        
        int[] arr = {1, 2, 3, 4, 5};
        
        //getComponentType()返回你数组里面装的数据的数据类型的类名称。这里也就是int
        Class<?> c = arr.getClass().getComponentType();    
        
        System.out.println("数组类型:" + c.getName());    //数组类型:int
        
        int len = Array.getLength(arr);
        System.out.println("数组长度:" + len);    //数组长度:5
        
        System.out.print("遍历数组:");
        
        for (int i = 0; i < len; i++) {
            System.out.print(Array.get(arr, i) + " ");    //遍历数组:1 2 3 4 5 
        }
        
        System.out.println();
        
        System.out.println("修改第三个数据前:" + Array.get(arr, 2));    //修改第三个数据前:3
        Array.set(arr, 2, 10);
        System.out.println("修改第三个数据前:" + Array.get(arr, 2));    //修改第三个数据前:10
    }
}